Various treatments are given to concrete floors and other surfaces having the same or similar makeup, for imparting decorative coloration to the surfaces, which surfaces are subsequently sealed to protect the underlying coloration. In a method of the present disclosure the coloration and sealing are imparted simultaneously.
Generally, there are two categories of concrete stains: reactive and non-reactive. The former category includes the use of chemical stains which are typically water-based acidic solutions containing metallic salts that react with the concrete's lime content. Once the chemical reaction takes place, the stain forms a permanent bond with the concrete and won't chip off or peel away.
Acid staining is reactive and transforms an ordinary concrete slab into a unique and beautifully imperfect floor. No two floors treated with acid staining are ever alike because every slab absorbs the color differently. Color differences may be evident from one room to the next—or even from one side of the same room to the other, because the original concrete may have been poured from different batches, even if poured at the same time. An acid stain process renders varying degrees of intensity, creating multi-hued color variations that appear perfectly aged. Therefore one should expect variability, not uniformity from acid staining of concrete. Such staining achieves beauty in an “Old World” imperfect way.
The acid staining process is effected by creating a chemical reaction on and within the concrete. Acid in the solution opens up the pores of the concrete, and metallic salts, also present in the solution, react with lime, an ingredient of cement. Because it actually creates the color in the concrete as opposed to merely on the concrete, there is no layer of pigment and thus the finish cannot peel, and the color is permanent. It may fade or dull slightly, but it is there for the life of the concrete.
Scoring or cutting shallow lines in the concrete, often in a large square or diagonal “tile” pattern, is an attractive option for acid-stained floors. The score lines can be grouted (i.e. filled) if desired, but are usually left open, for mortar grout is one of the things most consumers find least attractive—and troublesome.—about tile. Additionally, there are known in the art special saw blades designed for scoring which create a square groove. This effect is much more attractive than that produced by an ordinary narrow blade, which produces a shallow “V” type of cut.
Acid stained surfaces are usually sealed to enhance the color and to prevent staining of the unwanted kind, e.g. from spills and such. There are pros and cons to the different types of sealers available. Solvent-based sealers increase the depth and intensity of the color and are fairly glossy. When an application calls for a solvent-based sealer, a 100% acrylic ‘breathable’ sealer specially formulated for use on stained concrete is sometimes employed.
For many years, decorative concrete contractors have been using acid-based chemical stains to achieve rich, earth-toned color schemes resembling natural stone, marble, wood, or even leather. But today, contractors are no longer limited to earthy shades. Newer products on the market, such as water-based and solvent-based concrete dyes, are greatly expanding the artist's palette with colors ranging from soft pastels to vivid reds, oranges, yellows, and purples.
Concrete stain does more than add color. Rather than produce a solid, opaque effect like paint or colored coatings, stains permeate the concrete to infuse it with rich, deep, translucent tones. Depending on the color and application techniques used, the results can mimic everything from polished marble to tanned leather to natural stone or even stained wood.
Unlike stains, which react chemically with the calcium species (lime, et al.) present in concrete, dyes are non-reactive and impart color by penetrating concrete or other porous cementitious surfaces. Dyes are much smaller in particle size than chemical stains or acrylic stains, thus allowing for easier penetration and color saturation while leaving less residue on the surface. The small dye particles fill the pores of the concrete and are very hard to remove, making dyes nearly as permanent as acid stains. Because there is virtually no residue, minimal cleanup is required, greatly speeding the application process. Concrete dyes also provide permanent translucent penetrating color to concrete. Unlike acid stain, dyes do not chemically react with the concrete, and thus can be more predictable. They are generally more vivid in color as well, but can be diluted to soften or lighten the tone. They can be combined with other colors to produce custom hues in mottled and variegated effects. Dyes can also be applied to produce more of a monotone effect.
Dyes are available in water-based or solvent-based formulations and produce looks ranging from monotone to translucent, depending on how they are applied. Water-based dyes typically produce more marbling and variegation (similar to the look of a chemical stain), while solvent-based dyes tend to be more monotone and uniform in color. Some manufacturers' water- and solvent-based dyes can be combined to produce special color effects. The downside to dyes is that they penetrate very fast, leaving little room for error during application. Also, dies are generally not stable to ultraviolet light, and most manufacturers recommend indoor use only.
In the non-reactive category are water-based acrylic stains that don't rely on a chemical reaction to impart color. Instead, they are formulated to penetrate the concrete surface and deposit their pigment particles in the open pores. Non-reactive stains have grown in popularity in recent years because they are available in a much broader palette of colors than acid stains, and are easier to apply. However, the non-reactive stains do not produce the same variegated, translucent color tones characteristic of acid stains. The color effects tend to be more opaque and more uniform. Water-based urethane sealers are also non-reactive towards a concrete substrate and are sometimes employed as they provide a softer sheen and often a more natural appearance with less color intensification. Urethane sealers are more durable than acrylics, but acrylics are less expensive and easier to apply and re-apply than urethanes.
Once the desired color effects have been achieved, the floor or other substrate is sealed, usually with two coats of a solvent-based sealer. Following that, application of a wax to serve as a “sacrificial layer” for foot traffic to extend and maximize the life of the sealer is sometimes laid down using conventional techniques.